Customer Specific Special Order Set

Last May I sent you some drawings for a set of Lotus twin cam pistons for your assessment. After a lot of delays I now have the new crank which is a work of art,  so I’m ready to order the pistons. I’ll attach the drawings which have the bore size at a nominal 89.0mm. It’s actually 3.504”. I’m assuming that because they are to have piston-guided rods with a small end width of .725” we’ll have to use symmetrical forgings. 

So, along with the drawings these are the specs.

4 pistons identical - (no RH / LH) with rings, pins and locks Bore size 3.504”

Pin height 23.25mm

Thrust  to inlet side

2 ring, Zero-gap compression ring, radial gas porting.

Piston-guided rod, small end width .725” Pin dia  21mm. (Honda rod) Small end wall thickness 5.0mm

Round wire locks

Crown vol 16.5cc

Thermal and friction coatings.

The drawings show the valve pockets in relation to the pin centre. Please check that this works out at not less than 5.1mm for the inlet, 1.85mm for the exhaust, measured vertically from the deck height of the piston. (At the valve angle of 27º these measurements would be 5.65mm and 1.85mm respectively from the deck.)